Known in the art are various apparatus used to purify fluids by virtue of a magnetic or electric field which removes the minute impurities present in the fluid. So, there is known a separator for separating fluids from particulate material, incorporating a cylindrical housing with an internal partition arranged so as to form two chambers each representing a segment of a circle in cross section, one being filled with a ferromagnetic filtering packing and the other being void (cf. USSR Inventor's Certificate No. 698,658; published on Nov. 25, 1979). A means of magnetization in the form of a solenoid surrounding the housing from the outside sets up a magnetic field around the housing. A space at one end of the housing connects the chambers to each other and pipes at the top of the other end of the housing admit and discharge a fluid medium. On entering the void chamber, the fluid medium is exposed to the magnetic field set up therein with the result that the ferromagnetic particles contained in the fluid grow larger and continue to grow so when the fluid enters the connecting space. In the chamber containing the ferromagnetic packing, the ferromagnetic particles are separated from the fluid.
However, the known apparatus fails to separate from the fluid the bulk of electrically charged particles which do not belong to the ferromagnetic kind; these are removed only partially, being accidentally carried away by the ferromagnetic particulate material.